FCC challenge not accepting code, but works fine on vscode

[Bponthemove]

Trying to finish this challenge. I’ve done the code in vscode (in strict) and the return value is what is should be, however when I copy/paste it to the fcc site, it does not pass the challenge.
Its probably something stupid, however I’ve been going over and over it and cant find the issue.
code:

'use strict';

function alphabetUpper(x) {

    switch(x) {

        case 'N':resultArray.push('A');

        break;

        case 'O':resultArray.push('B');

        break;

        case 'P':resultArray.push('C');

        break;

        case 'Q':resultArray.push('D');

        break;

        case 'R':resultArray.push('E');

        break;

        case 'S':resultArray.push('F');

        break;

        case 'T':resultArray.push('G');

        break;

        case 'U':resultArray.push('H');

        break;

        case 'V':resultArray.push('I');

        break;

        case 'W':resultArray.push('J');

        break;

        case 'X':resultArray.push('K');

        break;

        case 'Y':resultArray.push('L');

        break;

        case 'Z':resultArray.push('M');

        break;

        case 'A':resultArray.push('N');

        break;

        case 'B':resultArray.push('O');

        break;

        case 'C':resultArray.push('P');

        break;

        case 'D':resultArray.push('Q');

        break;

        case 'E':resultArray.push('R');

        break;

        case 'F':resultArray.push('S');

        break;

        case 'G':resultArray.push('T');

        break;

        case 'H':resultArray.push('U');

        break;

        case 'I':resultArray.push('V');

        break;

        case 'J':resultArray.push('W');

        break;

        case 'K':resultArray.push('X');

        break;

        case 'L':resultArray.push('Y');

        break;

        case 'M':resultArray.push('Z');

        break;

    }

}

const resultArray = [];

let result = '';

function rot13(str) {

    let characters = str.split('');

    for (let i=0; i<characters.length; i++) {

        if (characters[i].match(/[a-z]/i)) {

            alphabetUpper(characters[i]);

        } else {

            resultArray.push(characters[i]);

        }

    }

    for (let i=0; i<resultArray.length; i++) {

        result = result + resultArray[i];

    }

    return result;

}

//end

Many thanks!

[ilenia]

can you please share the link for this challenge?

[Bponthemove]

freeCodeCamp.org

[Jagaya]

So how you would test it is by copying ALL test cases into the code-window, console.log them and see what is happening.

The error is quite simple: It’s called “global variables” → every time the function is called, it’s adding to “result” and the “result_array”. Meaning every call includes ALL PREVIOUS results in the array and double that in the result.

[Bponthemove]

that makes sense. Thanks, I didn’t think about that.

[Jagaya]

Yeah it’s a hard to spot error - and a good reminder as to why you should NEVER use global variables